/--------CREATING SIMPLE SHELL PROJECT -----/ This simple shell displays a prompt and waits for user to insert/type in coomands to the terminal.

Resources Read or watch:

Unix shell Thompson shell Ken Thompson Everything you need to know to start coding your own shell concept page man or help:

sh (Run sh as well)

Requirements General Allowed editors: vi, vim, emacs All your files will be compiled on Ubuntu 20.04 LTS using gcc, using the options -Wall -Werror -Wextra -pedantic -std=gnu89 All your files should end with a new line A README.md file, at the root of the folder of the project is mandatory Your code should use the Betty style. It will be checked using betty-style.pl and betty-doc.pl Your shell should not have any memory leaks No more than 5 functions per file All your header files should be include guarded Use system calls only when you need to (why?) Write a README with the description of your project You should have an AUTHORS file at the root of your repository, listing all individuals having contributed content to the repository. Format, see Docker GitHub *There should be one project repository per group. If you and your partner have a repository with the same name in both your accounts, you risk a 0% score. Add your partner as a collaborator. *

Compilation Your shell will be compiled this way:

gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh

TASK 0 Write a beautiful code that passes the Betty checks TASK 1 Write a UNIX command line interpreter.

Usage: simple_shell Your Shell should:

Display a prompt and wait for the user to type a command. A command line always ends with a new line. The prompt is displayed again each time a command has been executed. The command lines are simple, no semicolons, no pipes, no redirections or any other advanced features. The command lines are made only of one word. No arguments will be passed to programs. If an executable cannot be found, print an error message and display the prompt again. Handle errors. You have to handle the “end of file” condition (Ctrl+D) You don’t have to:

use the PATH implement built-ins handle special characters : ", ', `, , *, &, # be able to move the cursor handle commands with arguments execve will be the core part of your Shell, don’t forget to pass the environ to it…

TASK 2 Handle command lines with arguments TASK 3 Handle the PATH fork must not be called if the command doesn’t exist

TASK 4 Implement the exit built-in, that exits the shell Usage: exit You don’t have to handle any argument to the built-in exit

TASK 5 Implement the env built-in, that prints the current environment TASK 6 Write your own getline function Use a buffer to read many chars at once and call the least possible the read system call You will need to use static variables You are not allowed to use getline You don’t have to:

be able to move the cursor

TASK 7 You are not allowed to use strtok TASK 8 handle arguments for the built-in exit Usage: exit status, where status is an integer used to exit the shell

TASK 9 mplement the setenv and unsetenv builtin commands

setenv Initialize a new environment variable, or modify an existing one Command syntax: setenv VARIABLE VALUE Should print something on stderr on failure unsetenv Remove an environment variable Command syntax: unsetenv VARIABLE Should print something on stderr on failure

TASK 10 Implement the builtin command cd:

Changes the current directory of the process. Command syntax: cd [DIRECTORY] If no argument is given to cd the command must be interpreted like cd $HOME You have to handle the command cd - You have to update the environment variable PWD when you change directory man chdir, man getcwd

TASK 11 Handle the commands separator ; TASK 12 Handle the && and || shell logical operators TASK 13 Implement the alias builtin command Usage: alias [name[='value'] ...] alias: Prints a list of all aliases, one per line, in the form name='value' alias name [name2 ...]: Prints the aliases name, name2, etc 1 per line, in the form name='value' alias name='value' [...]: Defines an alias for each name whose value is given. If name is already an alias, replaces its value with value

TASK 14 Handle variables replacement Handle the $? variable Handle the $$ variable

TASK 15 Handle comments (#)

TASK 16 Usage: simple_shell [filename] Your shell can take a file as a command line argument The file contains all the commands that your shell should run before exiting The file should contain one command per line In this mode, the shell should not print a prompt and should not read from stdin